1. Field of the Invention
The present invention relates to an image forming apparatus. More particularly, the present invention relates to an electrostatic latent image forming medium for forming an electrostatic latent image using an optical shutter array and an image forming apparatus having such electrostatic latent image forming medium.
2. Description of the Related Art
In general, electrophotographic image forming apparatuses, such as copiers, laser printers, and facsimile machines, print an image by forming an electrostatic latent image on a photosensitive medium, such as a photoconductive drum or a photoreceptor belt, using a laser scanning unit (LSU), developing the electrostatic latent image using a developing agent having a predetermined color, and transferring the developed image onto a sheet of paper.
FIG. 1 is a perspective, schematic view of a conventional electrophotographic image forming apparatus including an LSU.
Referring to FIG. 1, the conventional image forming apparatus includes a photoconductive drum 20 on a surface of which an electrostatic latent image is formed, an LSU 10 scanning a laser beam to form the electrostatic latent image on the surface of the photoconductive drum 20, and a toner supply roller 30 supplying toner to the electrostatic latent image formed on the surface of the photoconductive drum 20.
The LSU 10 includes a laser diode (LD) 11 emitting a laser beam, a polygon mirror 12 scanning the laser beam emitted from the LD 11, a focusing lens 13 focusing a laser beam reflected by the polygon mirror 12, and a reflective mirror 14 reflecting a laser beam passing through the focusing lens 13 to form an electrostatic latent image on the surface of the photoconductive drum 20.
When the LSU 10 scans a laser beam onto the surface of the photoconductive drum 20 charged with a predetermined potential, the electric charges in a portion of the surface of the photoconductive drum 20 onto which the laser beam is scanned disappear, i.e., the electric charges become neutralized. Accordingly, an electrostatic latent image with a potential different from potentials of other portions of the surface of the photoconductive drum 20 is formed in the portion onto which the laser beam is scanned. Toner supplied by the toner supply roller 30 is selectively adhered to the electrostatic latent image by an electrostatic force. Thus, the electrostatic latent image is developed into a desired image. The image developed on the photoconductive drum 20 is transferred to a sheet of print paper P and then fixed on the sheet of print paper P by a fixing unit (not shown).
The LSU 10 has a complicated structure, and consequently the size of the conventional image forming apparatus is large, and the manufacturing costs thereof are high. Accordingly, there is a limitation in realizing a compact and inexpensive image forming apparatus using the LSU 10.
Also, since the LSU 10 scans a laser beam and forms an electrostatic latent image in a line-by-line manner while the polygon mirror 12 is rotated by a motor (not shown), it is difficult to increase print speed by reducing the time spent on scanning the laser beam. Since the rotation speed of the polygon mirror 12 is limited to a maximum of 55,000 rpm due to vibrations and noises caused by the rotation of the polygon mirror 12 of the LSU 10, maximum print speed using an LSU is limited by this limitation in rotational speed of the polygon mirror 12.